The Collaborative International Dictionary of English v.0.48:

Magniloquent \Mag*nil"o*quent\, a. [L. magnus great + loquens,
   -entis, p. pr. of loqui to speak. See Magnitude,
   Loquacious.]
   Speaking pompously; using swelling discourse; bombastic;
   tumid in style; grandiloquent. -- Mag*nil"o*quent*ly, adv.
   [1913 Webster]

WordNet (r) 3.0 (2006):

magniloquently
    adv 1: in a rhetorically grandiloquent manner; "the orator spoke
           magniloquently" [syn: grandiloquently,
           magniloquently]